1. Field of the Invention
The present invention generally relates to semiconductor integrated circuits, and particularly relates to a semiconductor integrated circuit having an error correction function.
2. Description of the Related Art
During the days in which semiconductor technologies were not yet matured, the reliability of flip-flops inside semiconductor circuits were low, resulting in the destruction of data stored in the flip-flops in some cases. The reason why such data destruction occurred may be attributable to the low reliability of circuit operations, or may be attributable to radiation emitted from a metal contained in semiconductor packages. Since the possibility of data destruction in flip-flops was small, a countermeasure was taken by performing a parity check on the data of flip-flops so as to suspend the system upon error detection, for example.
At the present day, the problem of having the data stored in flip-flops being destroyed is no longer in existence due to the development of semiconductor technology. Even with the semiconductor integrated circuits manufactured by use of the state-of-the-art semiconductor technology, however, the existence of the phenomenon called “soft error” is known in the case of DRAM, for example. This phenomenon is attributable to high-energy neutrons resulting from cosmic rays (i.e., neutrons as secondary particles generated upon reaction between positrons included in the cosmic rays and atomic nucleus contained in the atmosphere). In this phenomenon, bits stored in memory cells are changed by electric charge resulting from ions that are generated by the collisions between high-energy neutrons resulting from cosmic rays and silicon atomic nucleus because the DRAM memory cells consist of minute capacitance. In the case of flip-flops, however, the HIGH/LOW logic state of nodes of a cross-coupling circuit stores data. Unlike the DRAM, thus, data is never inverted by such energy as small as that of neutrons resulting from cosmic rays.
In the future, the size of circuit elements and the width of cross-connects will be further reduced due to the development of semiconductor technology. As such progress is made, it is expected that flip-flops used in semiconductor integrated circuits may suffer data destruction due to high-energy neutrons resulting from cosmic rays. In this case, the frequency of such data destruction is expected to be relatively high, so that a countermeasure that suspends a system upon error detection will not be suitable.
[Patent Document 1] Japanese Patent Application Publication No. 2002-251898
Accordingly, there is a need for a semiconductor integrated circuit with flip-flops providing an increased data reliability.